And while Pamela admitted that the Scot's diagnosis had come as "a shock", she has kept fans updated as he continues treatment, praising his determination.

"Billy is actually doing really well," she wrote in a recent article. "He continues the voice exercises that help to maintain his vocal texture, but that would be necessary even if he didn't have Parkinson's.

"He trains hard in the gym. He continues to tour, to do movies and TV series, and is frankly as funny as he's ever been."